Petrophysical Analysis of Reservoirs Rocks at Mchungwa Well in Block 7 Offshore, Tanzania: Geological Implication on the Reservoir Quality
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Date
2018
Journal Title
Journal ISSN
Volume Title
Publisher
Open Journal of Geology
Abstract
The present work highlights the results of the study conducted to estimate the
petrophyiscal properties of the Mchungwa well with the aim of assessing the
quality of reservoirs rocks. A set of well logs data from Mchungwa well were
used for the analysis that involved identification of lithology, hydrocarbon
and non-hydrocarbon zones and determinations of petrophysical parameters
such as shale volume, porosity, permeability, fluid saturation and net pay
thickness. This study was able to mark six sandstone zones with their tops and
bases. Of the six zones hydrocarbon indication was observed on four zones
from which estimation of petrophysical parameters was done to assess the reservoirs
quality. The petrophysical parameters across the four reservoirs yield
an average shale volume ranging from 0.08 to 0.15 v/v. The porosity ranges
from 7% to 23%, indicating a fair to good porosity sandstone, while permeability
ranges from 0.01 to 6 mD. The porosity and permeability results suggest
that the quality of the sandstone reservoirs identified at Mchungwa well is
poor. Fluid types defined in the reservoirs on the basis of neutron-density log
signatures and resistivity indicate a mixture of water and gas. However, high
water saturation (50% - 100%) indicates that the proportion of void spaces
occupied by water is high, thus, indicating low hydrocarbon saturation of
2.4%, 17.9%, 19.2% and 39.3%. Generally the results show that hydrocarbon
potentiality at Mchungwa well is extremely low because of small net pay
thickness and very low hydrocarbon saturation. This could be attributed to
the geology of the surrounding area where low hydrocarbon saturation suggest
the presence of non-commercial volumes of either migrant gas or gas
generated from the interbedded claystone sediments, which are dominant in
the observed well.
Description
Keywords
Offshore, Tanzania, Hydrocarbon, Reservoir, Petrophysical